Jimmy Carter - Afghanistan

In the meantime, in December 1979, the Soviets mounted a large-scale
invasion of Afghanistan to protect its Marxist regime. Washington
interpreted this as an extension of their ambitions and a threat to
American interests in the Persian Gulf area and responded with various
forms of pressure, including a grain embargo, a boycott of the Moscow
Olympics, reestablishment of registration for the military draft, warnings
against any efforts to gain control of the Persian Gulf area, and a
sizable military buildup. Carter had embraced Brzezinski's very
negative view of the Soviet Union, but the pressures did not persuade the
Soviets to withdraw, and the episode doomed SALT II.